Develop Reference

tools:listheader doesn't work although tools:listitem does

I have a fragment layout that contains the following code:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".BlankFragment">
<ListView
android:id="#+id/blankList"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:listheader="#layout/menu_header"
tools:listitem="#layout/fragment_item" />
</FrameLayout>
My fragment_item contains the following code:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="bottom"
android:orientation="horizontal"
android:background="#f0f0f0">
<ImageView
android:id="#+id/image_menu"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:paddingBottom="3dp"/>
<TextView
android:id="#+id/content"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="#dimen/menu_article_text_size"
android:layout_marginStart="16dp"
android:textAppearance="?attr/textAppearanceListItem" />
</LinearLayout>
My menu_header contains the following code:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.CardView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:elevation="12dp"
android:id="#+id/view2"
app:cardCornerRadius="40dp"
android:layout_centerHorizontal="true">
<ImageView
android:layout_height="80dp"
android:layout_width="match_parent"
android:id="#+id/imageView1"
android:src="#drawable/ic_launcher_background"
android:scaleType="centerCrop"/>
</android.support.v7.widget.CardView>
</LinearLayout>
My problem is that for some reason when I run it the app the fragment works, the list appears and the items of it are fine, but the header simply isn't there.
any help anyone?
* IMPORTANT FACT *
on the preview, it does work but it doesn't when I run it

My problem is that for some reason when I run it the app the fragment
works, the list appears and the items of it are fine, but the header
simply isn't there.
IMPORTANT FACT * on the preview, it does work but it doesn't when I run it
=> Looks like you have misunderstood about tools attribute. Those are design time attributes, means that it's helpful while designing layouts. Yes those are not meant for runtime and so obviously it won't be appeared in app.
To clarify it by giving you an example, android:text="Hello World and tools:text="Hello World". You should put demo/testing data in layout using tools attribute so user will not be seeing those data but it will be helpful to developers to see that there are views available in layout. In fact, they can adjust margins, paddings and all other layout design time operations!

How to make scrollable Items within a scrollable listview?

I have small database which populates data into a listview which uses other layout as provided below to show the data.
What happens is if the 1st field's text is more than two lines, the text starts hiding. So I thought i would make that listview's each row scrollable. Though it shows a scroll bar but nothing happens.
This is the layout which is used by listview
<?xml version="1.0" encoding="utf-8"?>
<ScrollView
android:layout_height="75dp"
android:layout_width="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="75dp"
xmlns:android="http://schemas.android.com/apk/res/android">
<TextView
android:id="#+id/desc_d"
android:layout_width="165dp"
android:layout_height="match_parent"
android:layout_alignParentStart="true"
android:text="Description"
android:gravity="center"
android:textAppearance="#android:style/TextAppearance.Large"/>
<TextView
android:id="#+id/cate_d"
android:layout_width="70dp"
android:layout_height="match_parent"
android:gravity="center"
android:layout_toEndOf="#id/desc_d"
android:text="others"
android:textAppearance="#android:style/TextAppearance.Large" />
<TextView
android:id="#+id/date_d"
android:layout_width="70dp"
android:layout_height="match_parent"
android:gravity="center"
android:layout_toEndOf="#id/cate_d"
android:text="16/11/2017"
android:textAppearance="#android:style/TextAppearance.Large" />
<TextView
android:id="#+id/amt_d"
android:layout_width="80dp"
android:layout_height="match_parent"
android:gravity="center"
android:layout_toEndOf="#id/date_d"
android:text="100000"
android:textAppearance="#android:style/TextAppearance.Large" />
</RelativeLayout>
</ScrollView>
My MainActivity layout has a listview which is also scrollable and uses above layout.
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:descendantFocusability="beforeDescendants"
android:focusableInTouchMode="true"
android:keepScreenOn="false"
android:scrollbarAlwaysDrawHorizontalTrack="false"
android:scrollbarAlwaysDrawVerticalTrack="false"
tools:context="apps.harry.expensedata.MainActivity">
<Button
android:id="#+id/add_expense_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:layout_marginTop="24dp"
android:onClick="addExpenseClick"
android:text="#string/button_1"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="#+id/view_expense_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="24dp"
android:onClick="viewClick"
android:text="#string/button_2"
app:layout_constraintStart_toEndOf="#+id/add_expense_btn"
app:layout_constraintTop_toTopOf="parent" />
<RelativeLayout
android:id="#+id/relativeLayout"
android:layout_width="match_parent"
android:layout_height="406dp"
android:layout_marginTop="84dp"
app:layout_constraintTop_toTopOf="parent"
tools:layout_editor_absoluteX="0dp">
<ListView
android:id="#+id/list_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
tools:layout_editor_absoluteX="8dp"
tools:layout_editor_absoluteY="248dp" />
</RelativeLayout>
</android.support.constraint.ConstraintLayout>
</ScrollView>
Here's the screen shot of the APP
As you can see there's a scroll bar available for each row in that layout, but nothing happens when I scroll.Please suggest me how this could be achieved.

This is not a solution suggestion for your scrolling problem, but due to user experience you should consider to not habe scrollable list items inside a scrollable list.
See Material Guidelines for this. Here is a little excerpt.
List tiles may contain up to three lines of text, and text length may vary between tiles in the same list. To display more than three lines of text, use a card.
Place the most distinguishing content on the left of the tile and the least distinguishing content on the right.
Specifications:
The majority of space on a list tile should be dedicated to the primary action
Place the most distinguishing content towards the left of the tile
In tiles with multi-line content, place the most distinguishing content in the first line
Place supplemental actions on the right side

Try using maxLines and minLines as attributes for the TextView to accommodate all the data.

Make scrollView Height="wrap_content" instead of fixed size. maybe useful

Google defined in their guidelines do not use scrollview inside of scrollview and it is more then simply guidelines it doesnt work properly. and you see that case. Tbe solution is set to your listitem height as wrap_content and the best practices is as was mentioned above do not use listitems with more than 2-3 lines of text. take a look into materisl design guide to see the dimensions of list items

I would suggest you to can change your custom list item height to wrap_content and then you don't need scrolling.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="horizontal"
android:padding="10dp">
<TextView
android:id="#+id/decription"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="center"
android:hint="decription" />
<TextView
android:id="#+id/whatFor"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="center"
android:hint="whatFor" />
<TextView
android:id="#+id/date"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="center"
android:hint="date" />
<TextView
android:id="#+id/amount"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="center"
android:hint="amount" />
</LinearLayout>
Your output will be like below image.
I hope your issue will be resolved and if you still have any query then please ask.

ConstraintLayout automatically resized by Android Studio

I'm new to Android and I've got problems designing a layout in Android Studio. I've found many related questions but none of them worked. Values of constraints are always hardcoded in dp by Android Studio according to the current preview size (Pixel, Nexus 7...).
Code I write in the XML editor (that works just fine on my phone):
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.meanstreet.note.Slider
android:id="#+id/slider"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.meanstreet.note.MainActivity">
<RelativeLayout
android:id="#+id/menu"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<Button
android:id="#+id/bold"
style="?android:attr/buttonBarButtonStyle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:text="#string/bold_button" />
...
Code changed after I went to the Design tab (that doesn't fit to my phone screen):
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.meanstreet.note.Slider
android:id="#+id/slider"
android:layout_width="344dp"
android:layout_height="495dp"
tools:context="com.meanstreet.note.MainActivity"
tools:layout_editor_absoluteY="8dp"
tools:layout_editor_absoluteX="8dp">
<RelativeLayout
android:id="#+id/menu"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<Button
android:id="#+id/bold"
style="?android:attr/buttonBarButtonStyle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:text="#string/bold_button" />
...
The Slider is a custom view that extends RelativeLayout.
The hardcoded values in Slider depend on the selected phone for the preview in Android Studio, and the view is now out of my phone (if the selected phone was bigger) or with big margins on right and bottom (if the selected phone was smaller).
This seems very weird to me: I can still avoid going to the Design tab, that way the code won't be changed and will work on any device, but that's annoying.
Why is Android Studio behaving like that ? How can I have the width and height to stay at "match_parent", and so have the right size on any phone ?
Thanks in advance for help.

match_parent is not supported for elements inside ConstraintLayout. Instead you can do;
Set the Slider's width to 0dp.
Add constraints to left and right with these attributes.
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
This way you can stretch that view horizontally. You can do the same thing vertically with same logic.
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.meanstreet.note.Slider
android:id="#+id/slider"
android:layout_width="0dp"
android:layout_height="495dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
tools:context="com.meanstreet.note.MainActivity"
tools:layout_editor_absoluteY="8dp"
tools:layout_editor_absoluteX="8dp">
<RelativeLayout
android:id="#+id/menu"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<Button
android:id="#+id/bold"
style="?android:attr/buttonBarButtonStyle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:text="#string/bold_button" />

Android layout anomaly - actual layout not complying with Android Studio appearance.

I am trying to write an application with two separate views of graphical data - one as an X-Y graph. and the other an X vs T graph. I want the two to be arranged vertically, with the X-Y graph on top. I have written an extension to the View class which manages the plotting, and that is not the problem.
I initially used a RelativeLayout:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:custom="http://schemas.android.com/apk/res-auto"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/content_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#CCCCFF"
android:orientation="vertical"
android:gravity="center_horizontal">
<RelativeLayout
android:id="#+id/button_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal">
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="clearCanvas"
android:text="#string/btn1Text"
style="#android:style/Widget.Button" />
<Button
android:id="#+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="startPlot"
android:text="#string/btn2Text"
android:layout_toRightOf="#id/button1"
style="#android:style/Widget.Button" />
</RelativeLayout>
<co.android.bmd.chaoswithtime.CanvasView
android:id="#+id/plot_canvas"
android:layout_width="1000px"
android:layout_height="1000px"
android:textColor="#FFFFFF" />
<co.android.bmd.chaoswithtime.CanvasView
android:id="#+id/trend_canvas"
android:textColor="#FFFFFF"
tools:layout_below="#id/plot_canvas"
android:layout_height="500px"
android:layout_width="1000px" />
</RelativeLayout
According to the layout shown in Android Studio, this should give the required result:
X-T view overlaying the XY view:
I've tried a number of variants to get the alignment sorted out, but the only way to do it was to add a hefty top margin to the X-T view - not very satisfactory.
I can get what I want using a LinearLayout, but cannot figure out why the Relativelayout does not work (and why there is a difference between the preview in Android Studio and the emulated result from the same package. (The emulated result actually comes up on the real device as well.)
Can anyone come up with an explanation?

You have passed width and height in pixels, that means it's content and when you run your code it takes only 1000 pixels in screen.
Better is that you should use LinearLayout as parent of your custom view and use weight and weightSum. And pass match_parent width and height to LinearLayout.
you can try with below xml. this could help you.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:custom="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/content_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#CCCCFF"
android:gravity="center_horizontal"
android:orientation="vertical">
<RelativeLayout
android:id="#+id/button_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal">
<Button
android:id="#+id/button1"
style="#android:style/Widget.Button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="clearCanvas"
android:text="#string/btn1Text" />
<Button
android:id="#+id/button2"
style="#android:style/Widget.Button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="#id/button1"
android:onClick="startPlot"
android:text="#string/btn2Text" />
</RelativeLayout>
<LinearLayout
android:layout_below="#+id/button_bar"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:weightSum="3">
<co.android.bmd.chaoswithtime.CanvasView
android:id="#+id/plot_canvas"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="2"
android:textColor="#FFFFFF" />
<co.android.bmd.chaoswithtime.CanvasView
android:id="#+id/trend_canvas"
android:layout_height="0dp"
android:layout_weight="2"
android:textColor="#FFFFFF"
tools:layout_below="#id/plot_canvas"1
android:layout_width="match_parent" />
</LinearLayout>
</RelativeLayout

android GridView issue show rows

I'm working with gridView, each item has an image and a TextView in the footer.
All images have the same size, so I use match_parent or wrap_content as required.
But the screen only show one line and a half on items, it scroll, and that is perfect, but I would like to show two complete rows and then scroll.
Also, when I run the app in small devices, only show 1 line, I would like to show 2 lines always.
I tried to use this example, but it doesn't work to me because stop scrolling.
Here, some of my code XML
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#drawable/bg_app">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/black"
android:id="#+id/header"
android:padding="10dp">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/icon_back"
android:src="#drawable/ic_back" />
</RelativeLayout>
<com.xetux.util.ExpandableHeightGridView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:gravity="center"
android:horizontalSpacing="15dp"
android:isScrollContainer="true"
android:numColumns="3"
android:padding="10dp"
android:id="#+id/family_grid_view"
android:layout_below="#+id/header"
android:verticalSpacing="15dp"/>
<!--<GridView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="10dp"
android:id="#+id/family_grid_view"
android:horizontalSpacing="15dp"
android:verticalSpacing="15dp"
android:layout_below="#+id/header"
android:numColumns="3"/>-->
</RelativeLayout>
and each item XML:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/family_image"
android:background="#drawable/bg_family">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/black_transparency"
android:text="FAMILIA"
android:gravity="center"
android:id="#+id/family_name"
android:padding="10dp"
android:layout_alignParentBottom="true"
android:textColor="#color/white"
android:textSize="15sp"/>
</RelativeLayout>

I think your image size is big. You can checkout for supporting multiple screen tutorials. Try using small images for small screen.